Carbon nanotubes (CNTs) are of interest in utilization in various devices utilized in semiconductor constructions, including, for example, devices utilized in integrated circuitry (IC) and devices utilized in micro-electro-mechanical systems (MEMS). Carbon nanotubes are allotropes of carbon, and are cylindrical molecules. The cylinders may have maximum widths (e.g., diameters if the cylinders are circular in cross-section) of less than 100 nanometers, less than 50 nanometers, or even less than 2 nanometers; and may have lengths that are tens, hundreds, thousands, or even millions of times greater than the maximum widths.
Among the properties that make CNTs of interest are high chemical stability, high thermal stability, small size, and conductive properties that may be tailored to be either metal-like or semiconductor-like.
Although CNTs have properties that may make them suitable for incorporation into semiconductor devices, there are also numerous problems and difficulties encountered in attempting to incorporate CNTs into semiconductor devices. For instance, conductive properties of CNTs may be significantly altered if metals, oxides or other contaminants comingle with the CNTs.
An active area of interest in integrated circuitry is in attempting to transition from single level cells (SLCs) to multilevel cells (MLCs). MLCs differ from SLCs in the amount of data that may be stored in the devices. Specifically, an SLC device has only two different states (which may be identified as states 0 and 1), and thus stores only a single data bit. In contrast, an MLC device has at least four different states (which may be identified as states 11, 01, 00, and 10 for a four-state device), and thus stores at least two data bits. Accordingly, at least twice as much information may be stored in an MLC as can be stored in an SLC.
An interesting property of CNTs is that if a plurality of CNTs are bundled together, and arranged so that the CNTs cross one another throughout the bundle (in other words, are askew with one another rather than parallel to one another), the bundle may have four or more distinguishable electrical states. Accordingly, CNTs show promise for utilization in MLC devices. However, it is difficult to form MLC devices comprising CNT bundles in that the electrical properties of the CNT bundles may be significantly altered if contaminants enter the bundles.
It would be desirable to develop new methods for incorporating CNTs into semiconductor devices, and to develop new devices comprising CNTs.